Field of the Invention
The present invention relates to focus control in an image capturing apparatus such as a digital still camera or a digital video camera and in an optical apparatus such as an interchangeable lens, and particularly to focus control using both an imaging surface phase difference AF and a contrast AF.
Description of the Related Art
The imaging surface phase difference AF uses paired object images formed on an image sensor for image capturing of an object through an optical system. The paired object images have a shift amount corresponding to a focus state of an image capturing system constituted by the optical system and the image sensor. Then, the imaging surface phase difference AF further calculates a defocus amount of the image capturing system by using a shift amount (phase difference) between paired image signals obtained by photoelectrically converting the paired object images by the image sensor and moves a focus element by a drive amount calculated from the defocus amount to thereby acquire an in-focus state of the image capturing system.
On the other hand, the contrast AF extracts a high frequency component from an output of the image sensor which is obtained by photoelectrically converting an object image to acquire a contrast evaluation value representing a contrast state of the object image. Then, the contrast AF moves the focus element to an in-focus position at which the contrast evaluation value becomes a maximum (peak) value to thereby acquire an in-focus state.
Japanese Patent Laid-open No. 2010-256824 discloses an image capturing apparatus that fast and highly accurately achieves an in-focus state by moving a focus lens to a vicinity of a position (in-focus position) at which the in-focus state is acquired, on a basis of a focus detection result obtained by the phase difference AF and by then performing the contrast AF. Furthermore, the image capturing apparatus disclosed in Japanese Patent Laid-open No. 2010-256824 moves, when the focus detection result obtained by the phase difference AF has a high reliability, the focus lens to a closer position to the in-focus position on a basis of this focus detection result and then performs the contrast AF. This enables the in-focus state to be acquired faster.
However, as the image capturing apparatus disclosed in Japanese Patent Laid-open No. 2010-256824, performing the contrast AF after the phase difference AF may fail to acquire an in-focus state sufficiently fast because of a condition of an object such as a low contrast.